微塑料老化对四环素吸附行为的影响

微塑料吸附有机污染物会加剧其对水环境的污染.该研究以四环素（TC）为目标污染物，通过过硫酸老化聚乳酸（PLA）、聚对苯二甲酸乙二醇酯（PET）和聚丙烯（PP）3种微塑料，研究其对TC的吸附行为的影响.结果表明:①过硫酸盐老化使3种微塑料表面出现大量褶皱、碎片和沟壑，比表面积增大及含氧官能团含量显著提高.②原始PET和PP吸附TC的动力学过程符合准一级动力学模型，而PLA以及老化PET和PP均符合准二级动力学模型，属于化学吸附；PLA和PET对TC的吸附符合Langmuir等温吸附模型，以单分子层吸附反应为主，而老化PP则更符合Freundlich等温吸附模型；拟合参数中，老化PLA与PET最大表观吸附量分别可达2.293和3.617 mg/g.③pH对微塑料的吸附能力有较大的影响，且pH为7时对老化PP影响最大，其对TC的吸附值为1.214 mg/g.研究显示，微塑料作为TC的有效载体，其老化会加重对水体的迁移毒性作用. 

Effect of Aging on Adsorption of Tetracycline by Microplastics

The pervasiveness of microplastics that can adsorb organic pollutants may aggravate the contamination in the aqueous environment. In this study, three kinds of microplastics, polylactic acid (PLA), polyethylene terephthalate (PET) and polypropylene (PP), were aged by persulfate oxidation to investigate the effect of aging on the adsorption behavior of tetracycline. The results showed that there were a lot of wrinkles, fragments and gullies on the surface of the three microplastics after aging. At the same time, the specific surface area and oxygen functional groups were increased significantly. The adsorption data were well fitted by the pseudo-first-order kinetics for original PET and PP and the pseudo-second-order kinetics for PLA, aging PET and PP. The adsorption data were in accordance with the Langmuir isotherm and dominated by monomolecular layer adsorption reactions for PLA and PET, while aging PP adsorption was more in line with Freundlich adsorption. The fitting results showed that the maximum apparent adsorption capacity (q_max) PLA and PET for TC increased to 2.293 mg/g and 3.617 mg/g respectively after aging. In addition, pH had a great effect on the adsorption capacity of microplastics, and the adsorption values of PP for TC could reach 1.214 mg/g when pH=7. Therefore, microplastics can act as effective carriers of TC, and the carrier effect of aged microplastics may aggravate the toxic effect of migration to water bodies.